OpenSpec: add-project-clean-all-safe (batch worktree cleanup from the maintenance design packet) #9

Lane: openRepoProject-2

Governing record for the OpenSpec change add-project-clean-all-safe: the batch worktree cleanup feature (project clean <root> --all-safe) proposed from the merged project maintenance design packet (ideation/brainstorm/, PR #7 at da33d92; packet record #6).

Scope: one governed change under openspec/changes/add-project-clean-all-safe/ carrying the proposal, alignment review, council, clarifications, design, the spec deltas (MODIFIED and ADDED requirements on project-clean, project-clean-review-safety and project-command), and a governance tasks.md with exactly one Speckit handoff (feature 003). Branch deletion, cache disposal, remote queries, family traversal, bench, container and park integrations stay out, as the packet defers them. Any future paired-retirement extension is a MODIFIED requirement on project-clean (PR #2 decision record).

Baseline: origin/main da33d92; project and its tests unchanged since a040790. Sibling change add-project-overview depends on this one and is governed separately.

Done when: the change validates --strict, the proposal PR is ratified by Brett Heap and lands, and the Speckit feature is named in the handoff. Refs #6.